CITRIC ACID. 297 



been previously well washed out from the citrate 

 of lime, the crystals will be rhornboidal, and of a 

 bright light brown. Citric acid in this state is found 

 to answer extremely well as applicable to the arts, 

 but for some processes in these it is desirable to have 

 the acid quite pure ; and this last condition is always 

 requisite in medicine and domestic economy. To 

 produce this purity the crystals are dissolved in clear 

 water and boiled by steam heat, with the addition of 

 animal charcoal : the solution is then passed through 

 a flannel filter, and left for crystallization ; very 

 white and beautiful solid crystals in rhomboidal 

 prisms will be thus produced. 



In the autumn, the time when lemons come to 

 maturity, 4,000 lemons are required to furnish about 

 twenty gallons of juice : this juice, when good, gene- 

 rally gives eighteen pounds of dry citrate of lime, 

 and these again give ten pounds of good white crys- 

 tals of citric acid. When the juice employed has 

 been but recently expressed from the fruit, it is stated 

 that a gallon of lime juice yields from fourteen to 

 eighteen ounces of pure citric acid. 



The person who first prepared this acid in large 

 quantities in England sold it at a high price, in the 

 form of clear white crystals. The calico-printers 

 were supplied with this for many years, until the 

 demand becoming greater than the manufacturer's 

 ability to comply with it, he began to furnish his cus- 

 tomers with the brown crystals, that is, with the acid 

 in the first or second stage of crystallization. These 

 brown crystals he could of course afford to sell at a 

 much lower price. 



The discovery that citric acid could be used in its 

 impure state in calico-printing, caused those engaged 

 in that pursuit to turn their attention to the mode of 

 preparing it themselves ; and now most of the pro- 

 prietors of large establishments buy the plain lemon 



